Sample Size The main short-term endpoints of the study are both qualitative (lymph node yield, grade of specimen) and quantitative (operative time, cosmesis satisfaction, resumption of normal diet/intestinal function, length of hospital stay). Cancer-related survival is the main long-term primary end-point. The working hypothesis is that there will be no significant differences in this variable between SILS and conventional laparoscopic right hemicolectomy, but that differences in variables related to the short-term outcome (i.e. morbidity and duration of hospital stay) would favour SILS. We assume that a difference in cancer-related survival of less than 15% between treatments indicates an equivalent efficacy. Assuming a 70% 5-year cancer-related survival in the laparoscopic colectomy group, a minimum of 100 patients per group is required to show that both surgical techniques are equivalent with an α level of 0•20 and a β error of 0•05. Recruitment of patients is not expected to be difficult because evidence to date is convincing of at least equivalent outcome and we believe that most patients would hope to be assigned to the SILS group, with potentially shorter hospital stay, less pain and improved cosmesis. From a surgeon's perspective, SILS is technically feasible and represents only a slight modification of the conventional laparoscopic procedure.